In an optical fiber connection, for example, by welding or the like, cleaving the end surface of each optical fiber is required so that the end surface is at a right angle to the axial direction of the optical fiber, and the surface is flat and smooth to minimize light attenuation through the connection.
The optical fiber cleaver shown in Prior Art FIGS. 12A and 12B, for example, is a conventional optical fiber cleaver (see JP-A-7-81970).
The optical fiber cleaver 101 shown in Prior Art FIGS. 12A and 12B comprises a clamp stand 103 on one end of a base 102 that holds a jacket of a fiber-optic cable (not shown in the figure), a second clamp stand 105 on the other end of the base 102 that holds an optical fiber, and a blade 107 disposed on the base 102 between the clamp stand 103 and the second clamp stand 105 which cleaves the optical fiber.
Guide grooves 103a which receive jackets are formed in the upper surface of the clamp stand 103. Furthermore, a jacket clamp 104 is pivotally attached to the surface of the clamp stand 103 so that the jacket of a fiber-optic cable in the guide groove 103a is pressed and fastened in place by closing the jacket clamp 104. The clamp stand 103 imparts a tensile force in cooperation with the second clamp stand 105 to the fiber-optic cable. Specifically, the clamp stand 103 is slidable toward the blade 107 (axial direction of the optical fiber) during cleaving, and is biased away from the blade 107 by an elastic member (not shown in the figure).
A fiber clamp 106 is pivotally attached to the surface of the second clamp stand 105 so that the optical fiber is fastened by closing the fiber clamp 106.
In addition, the blade 107 is formed as a disk, and is fastened to a slider 108 that slides in a direction perpendicular to the axial direction of the optical fiber. The blade 107 is positioned underneath the optical fiber that is fastened to the clamp stand 103 and fiber clamp 106, so that the blade 107 initially partially cleaves the optical fiber by sliding in the direction perpendicular to the axial direction of the optical fiber.
Furthermore, as is shown in Prior Art FIG. 12A, a scale 109 for setting the cleaving length of an optical fiber is provided on the clamp stand 103.
When an optical fiber is to be cleaved by the optical fiber cleaver 101, the jacket clamp 104 and fiber clamp 106 are first opened, the jacketed part of the fiber-optic cable is fitted into one of the guide grooves 103a, and the optical fiber is placed on the second clamp stand 105. Next, the jacket clamp 104 is closed, and the clamp stand 103 is urged toward the blade 107 and stopped at a specified position. In this state, the fiber clamp 106 is closed. At this point, because the clamp stand 103 is biased away from the blade 107 by the built-in elastic member, a certain amount of tensile force is applied to the optical fiber. Then, when the blade 107 is slid in the direction perpendicular to the optical fiber axial direction, a cut is formed in the optical fiber, and the optical fiber is cleaved by the tensile force described above.
Moreover, the cleaver shown in Prior Art FIG. 13, is another example of a conventional optical fiber cleaver for cleaving optical fibers (see JP-A-2003-165740).
The optical fiber cleaver 201 shown in Prior Art FIG. 13 comprises a main body 202, a cover 203 pivotally attached to the main body 202, a pair of upper and lower clamps 204a, 205a and 204b, 205b that hold the optical fiber of a fiber-optic cable, a blade part 207 that slides in a direction perpendicular to the optical fiber and that initially partially cleaves the optical fiber, a holder 210 that holds the jacketed part of the optical fiber, and a pillow 208 that bends the optical fiber.
Here, the pair of upper and lower clamps 204a, 205a and 204b, 205b are constructed by fitting rubber into a metal stand part. The lower clamps 205a and 205b are installed a specified distance apart along an optical fiber axial direction on one end of the upper portion of the main body 202 while the upper clamps 204a and 204b are installed on the cover 203 in positions facing the lower clamps 205a and 205b. 
Furthermore, the blade 207 is disk shaped and is fastened to a slider 206 that slides in a direction perpendicular to the optical fiber. The blade 207 is disposed between the upper and lower clamps 204a, 205a and 204b, 205b. 
Moreover, the holder 210 is designed to be attached to a holder guide 209 formed on the other end of the main body 202.
In addition, the pillow 208 is installed on the cover 203, and works in conjunction with the blade 207 so that after the blade 207 initially partially cleaves the optical fiber, the pillow 208 bends the optical fiber and fully cleaves the optical fiber.
When optical fibers are to be cleaved by this optical fiber cleaver 201, the fiber-optic cables are first set in the holder 210, and the jacket at the end portions of the respective fiber-optic cables are removed to expose the optical fibers. Next, the cover 203 is opened, and the holder 210 is attached to the holder guide 209. Then, the cover 203 is closed, and slider 206 is slid causing the blade 207 to initially partially cleave the optical fibers. Then, the pillow 208 bends the optical fibers, causing propagation of the initial partial cleave and ultimately fracturing the optical fibers.
Furthermore, the optical fiber cleaver shown in Prior Art FIGS. 14A and 14B, for example, is another example of a conventional optical fiber cleaver for cleaving optical fibers (see JP-UM-A-63-135304).
The optical fiber cleaver 301 shown in Prior Art FIGS. 14A and 14B is devised as follows: namely, a spring 304 is interposed between a pair of first frames 302 and second frames 303 that can be opened and closed, where opening these frames allows placement of a fiber-optic cable 320 on the carrier 305 of the first frame 302. When the first and second frames 302 and 303 are closed, an optical fiber 322 of the fiber-optic cable 320 is cleaved by a blade 307 and a bending arm 308 while the optical fiber 322 is pressed and held by a press 306.
Here, the carrier 305 comprises a bender holder 310 attached to the free end of the first frame 302, a bender plate 311 having one end is attached to the surface of the bender holder 310, a rubber bender 312 attached to the surface of the bender plate 311, and a fiber guide 313 attached to the other ends of the bender plate 311 and rubber bender 312. Furthermore, a wide groove 314 in which the jacketed part 321 of the fiber-optic cable 320 is accommodated and a narrow groove 315 in which the optical fiber 322 of the fiber-optic cable 320 is accommodated are formed in the fiber guide 313.
Moreover, the blade 307 is attached to the second frame 303 so that this cleaver can swing in a direction perpendicular to an optical fiber axial direction. The blade 307 has the function of initially partially cleaving the optical fiber 322 while the optical fiber 322 of the fiber-optic cable 320 is pressed and held by the press 306 when the first and second frames 302 and 303 are closed.
In addition, the bending arm 308 is attached to the second frame 303. The bending arm 308 is devised as follows: namely, after the blade 307 initially partially cleaves the optical fiber 322, the bending arm 308 presses the fiber guide 313 to flex the carrier 305 downward, thus imparting a bending force to the optical fiber 322. When the optical fiber 322 is bent by the bending arm 308, the initial partial cleave propagates and results in the fracturing of the optical fiber 322.
Furthermore, the optical fiber cleaver shown in Prior Art FIGS. 15A through 15C, for example, is another example of a conventional optical fiber cleaver for cleaving optical fibers (see JP-UM-A-63-21905).
The optical fiber cleaver 401 shown in Prior Art FIGS. 15A through 15C comprises a spring plate 402 and an arm 403 pivotally attached to the spring plate 402. The spring plate 402 is provided with a guide 404 that guides the jacketed part 411 and optical fiber 412 of a fiber-optic cable 410, and a clamp 405 that fastens the end portion of the optical fiber 412 of the fiber-optic cable 410. Moreover, a slider 406 that can slide along the direction of length of the arm 403 is attached to the arm 403. A blade 407 that initially partially cleaves the optical fiber 412 of the fiber-optic cable 410 is provided at the lower end of slider 406. The slider 406 is fastened to a specified position of the arm 403 in a direction of length by a fastening screw 408. In addition, a scale 409 for confirming the position of the slider 406 is provided with markings at 5 mm intervals on a side surface of the arm 403 in the sliding range of the slider 406. Furthermore, a position confirming mark 406a is provided on a side surface of the slider 406, so that the cleaving length of the optical fiber 412 can be confirmed by reading the value of the scale 409 indicated by the position confirming mark 406a. 
When the fiber-optic cable 410 is to be cleaved by the optical fiber cleaver 401, the slider 406 is first moved to the position of a target cleaving length and fastened in place, the jacketed part 411 and optical fiber 412 (which is not covered by a jacket) of the fiber-optic cable 410 are set on the spring plate 402 in accordance with the guide 404, and the tip of the optical fiber 412 is pressed by the clamp 405. Next, the blade 407 is pressed against the optical fiber 412 of the fiber-optic cable 410 to initially cleave the optical fiber 412 by pressing the arm 403 down. Next, the blade 407 is released and the spring plate 402 is bent, so that the optical fiber 412 is fully cleaved.
However, the following problems have been encountered in the optical fiber cleaver 101 shown in Prior Art FIGS. 12A and 12B, the optical fiber cleaver 201 shown in Prior Art FIG. 13, the optical fiber cleaver 301 shown in Prior Art FIGS. 14A and 14B, and the optical fiber cleaver 401 shown in Prior Art FIGS. 15A through 15C:
Specifically, in the case of the optical fiber cleaver 101 shown in Prior Art FIGS. 12A and 12B, a certain amount of tensile force is applied to the optical fiber of the fiber-optic cable when the optical fiber is cleaved. Therefore, when the blade 107 is pressed against the optical fiber, there is a concern that the optical fiber may escape from the blade 107. Accordingly, it is difficult to form a stable cleaving in the optical fiber, and there are cases in which the cleaved surface is inclined or ripped which contributes to signal attenuation. Furthermore, the scale 109 for setting the optical fiber cleaving length is provided on the clamp stand 103, but there is no clear description of how to use the scale 109. Because the cleaving length of the optical fiber refers to the length of the optical fiber of a fiber-optic cable in which the jacket is removed at one end portion, cleaving the optical fiber involves moving the clamp stand 103 in toward the blade 107 after closing the jacket clamp 104. Therefore, the tip end of the jacketed part is hidden when the cleaving length is determined so that the cleaving length of the optical fiber cannot be determined using the scale 109.
Moreover, in the case of the optical fiber cleaver 201 shown in Prior Art FIG. 13, while the blade 207 is fastened to the slider 206, the pillow 208 is installed on the cover 203, undesirably complicating the cleaving mechanism of the optical fiber. Furthermore, the fastening position of the optical fiber by means of the holder 210 is fixed, undesirably limiting cleaving of an optical fiber to a single predetermined length.
In addition, in the case of the optical fiber cleaver 301 shown in Prior Art FIGS. 14A and 14B, because the fiber-optic cable 320 is not fastened on the side of the jacketed part 321, the process of cleaving the optical fiber 322 with blade 307 is unstable, resulting in cleaved surfaces which are inclined or ripped which contributes to signal attenuation. Furthermore, because only a certain location of the blade 307 contacts the optical fiber 322, the blade 307 has a short service life. Moreover, when the carrier 305 is repeatedly flexed downward by the bending arm 308, the rubber bender 312 undergoes plastic deformation into the shape of the letter “V” as a result of the repeated bending action of the rubber bender 312, so that there is a possibility that the blade 307 will no longer contact the optical fiber 322 at a right angle. As a result, cleaving the optical fiber 322 is unstable, resulting in cleaved surfaces which are inclined or ripped which contributes to signal attenuation. In addition, because the fastening position of the fiber-optic cable 320 is fixed, the optical fiber 322 can only be cleaved at a certain length.
Furthermore, in the case of the optical fiber cleaver 401 shown in Prior Art FIGS. 15A-15C, because the fiber-optic cable 410 is not fastened on the side of the jacketed part 411 (the fiber-optic cable 410 is merely guided in the guide 404), cleaving the optical fiber 412 by the blade 407 is unstable, resulting in cleaved surfaces that are inclined or ripped which contributes to signal attenuation. Moreover, because only a certain location of the blade 407 contacts the optical fiber 412, the blade 407 has a short service life. In addition, if the spring plate 402 is repeatedly bent over long-term use, the spring plate 402 undergoes plastic deformation into the shape of the letter “V,” so that there is a possibility that the blade 407 will no longer contact the optical fiber 412 at a right angle. As a result, cleaving the optical fiber 412 is unstable, resulting in cleaved surfaces that are inclined or ripped which contributes to signal attenuation. Furthermore, while the cleaving length of the optical fiber 410 can be set and confirmed by reading the value of the scale 409 indicated by the position confirming mark 406a, the process is cumbersome. Specifically, when the cleaving length is to be changed, it is necessary to temporarily loosen the fastening screw 408 to move the cleaver box 406 to the new position in the direction of length of the arm 403, and then to fasten the cleaver box 406 to the arm 403 by tightening the fastening screw 408. This operation is troublesome prevents easy changing of the cleaving length setting.